1. Technical Field of the Invention
The present invention relates to an image-processing device, an image-processing method and a solid-state image pickup device. In particular, the invention relates to an image-processing device that picks an image up with a solid-state image-pickup element, an image-processing method and a solid-state image pickup device thereof.
2. Description of the Related Art
A semiconductor image sensor is used for various kinds of image input devices. Recently, of such semiconductor image sensors, a MOS solid-state image-sensing device with a threshold voltage modulation system attracts attention since it provides high image quality attained by a CCD (charged coupled device) with low power consumption by a CMOS and restrains deterioration of an image quality and realizes high density and low cost.
Technology of a MOS solid-state image-sensing device with a threshold voltage modulation system is disclosed in the Japanese Patent Publication Laid-Open No. 11-195778 for example. In a MOS solid-state image-sensing device with a threshold voltage modulation system, three states such as initialization, accumulation and reading out are repeated such that an image signal based on charges for emitting light that are accumulated in a carrier pocket of each pixel can be pulled out. An initialization period is a period of discharging residual charges from a carrier pocket. An accumulation period is a period of accumulating charges in a sensor cell. A reading out period is a period of reading a volume of charge out with voltage modulation.
However, for example, if the gate voltage is boosted in order to increase a ratio of selected lines while in the state of an accumulation period for accumulating photo generated charges in a carrier pocket to non selected lines while in the sate of a reading out period for reading an image signal based on accumulated photo generated charges, holes are not selected sufficiently so as not to obtain good image quality.
However, the Japanese Patent Publication Laid-Open No. 11-195778 does not disclose a method of applying a gate voltage in order to obtain a good image quality in such case.
Therefore, the present invention is intended to provide an image-processing device that applies a gate voltage in order to obtain a good image quality, an image-processing method and a solid-state image pickup device thereof.